Sure, any self-respecting Pontiac speed freak can appreciate engines that produce big power numbers. As such they are part and parcel of most magazine engine buildup stories--seen any 2-barrel 326 builds lately? So to provide the most pertinent information, HPP photographs all of the parts that make the power production possible and discusses the reasons why they will work so well together based on the builder's knowledge, and the readers love it. But have we lost sight of the fact that in order for said engine to really run the number, it has to be assembled properly with great attention to detail? This means more than checking for proper clearances. We're talking about inspecting all of the parts before you install them, disassembling checking and reassembling component parts and going over each detail with an eye toward durability.
HPP recently had the opportunity to do just that as we followed a build-up on hobbyist Thom Greenwald's 455 HO engine at Jim Taylor Engine Service. To that end, the focus of this article is to illustrate which assembly techniques and tricks Taylor and his protege Mark Erney employ to add reliability to the engine and ease the building process. Jim's 30+ years of experience in the field is sure to provide some fresh insights for even the most seasoned hobbyist engine builder.
We will disclose a detailed list of the pertinent building specs in the next issue so that you can see the combination for yourself. For now, here are the basics. The engine in question consists of a 455 HO service replacement block with the obligatory nodular-iron crank held in by 4-bolt mains. A set of mildly ported 1972 7F6 heads will sit up top. A Crane hydraulic cam with 228* duration at .050, .485 lift with 1.52:1 ratio roller rockers and 112* lobe separation will be employed. According to Jim Taylor, "It will be a strong street engine with 9:1 compression that will be good for 425 horsepower." This, regardless of the induction system choice, as the owner is considering aftermarket fuel injection at this point.
Of special note is that fact that Jim employed a set of 1957 Pontiac forged rods for this project despite their reputation for being soft. How could he do it and promise reliability? And why is this rod worth it? Read on.
In this issue we will begin with the bottom end assembly. Given the amount of detail provided, we will continue with the bottom end in the next issue and then move onto the heads and valvetrain. Since we had a lot of ground to cover during the two-day shoot, in some instances photos were taken of other engines in the shop to illustrate a given procedure or technique. They will be identified in each case.
Of course, we chose to do this build-up on a 455 HO because readers love to see round port engines go together but all of the information given can be applied to any traditional Pontiac engine.
With the block returned from the machine shop (in this case a 4-bolt 400), the cam bearings are installed. Here you can see Mark Erney performing the #4 bearing installation. Care is taken to ensure that the oil feed hole is lined up with the oil feed vein from the mains in the block. Each bearing is beveled on one side to facilitate installation. The tool presses the bearing into place with help from a hammer. A centering cone at the front of the block ensures that the bearing is installed squarely. If it isn't, the cam won't spin freely. The toughest bearing is the front one because the cone cannot be used to square it. Much skill on the part of the installer is required to press the front bearing correctly.
Brass freeze plugs and oil plugs were installed next. The procedure is pretty standard. Permatex Aviation Form-A-Gasket is spread in the holes and the plugs are tapped into place. Brass is used because it doesn't rust. Block drain plugs are sealed with liquid Teflon. Note the block was returned from the machine shop with industrial primer on the outside. It was also delivered shrink wrapped for cleanliness. (Machining processes after hot tanking included; boring and honing, decking if needed and an align bore or hone if needed. A 400 block is shown.)
The through-the-block oil dipstick tube is installed next. Two important considerations here are a proper interference fit and the depth at which you install it. Jim has seen some aftermarket tubes that slide freely right through the hole, which is not good. Using a ground down 3/8-inch rocker stud, the tube is pressed into place by sliding the stud into the tube and tapping with a hammer. The thickness of the stud creates an interference fit in the tube, which will keep it from crushing, and the shoulder on the stud will keep the end of the tube from rolling during installation.
Measuring main bearing clearance was done at the machine shop using an inside micrometer on the main saddles with bearings in place and the caps torqued. An outside micrometer measured each journal. The journal measurement is subtracted from the saddle measurement and the result is the clearance, which should be .004 on this engine. Note that the running clearance will be .002 as the crank will be spinning supported by a film of oil that will center it in the bearings. Here we see the crankshaft endplay measurement. The crank is placed in the block with only the upper bearings in place, with either no main caps; just #1 and #5 caps; or with #1, 2, 3, and 5 caps installed. Then a dial indicator is mounted. A large screwdriver placed between the block and a counterweight. First the crank is pushed back and the dial indicator is preloaded and set to "0." Then the crank is pushed forward. The endplay measurement on the gauge is .007, which is within the tolerance range of .006-.011 recommended by Pontiac.
Next, the #4 main cap, which holds the thrust bearing, is torqued to spec, as shown, on a 400 engine and the endplay will be determined again to see if the measurement has changed. Jim warns that checking the endplay with no caps and then again after the thrust cap is installed is especially important when using aftermarket 4-bolt caps. If endplay measurement now is less than the first, you may have a tipped cap or a cap that is forward or back from the proper position. Both situations must be rectified before assembly continues. The thrust bearing must have 100 percent contact across the face. According to Jim, "It's very rare that the thrust surface is not perfect on a stock engine, but if it is out, you can true the thrust surface of the bearing by milling down one half. It's the backside that is critical, especially on a clutch car."
Shown is the radius (arrow), which is a strength union between the rod journal and the counterweight that is designed into the crank. According to Taylor, "Many times when you hear that a Pontiac crank has cracked in operation it is due to an inexperienced machinist who took out the radius when machining it." Note the chamfered oil holes and polished surface on this 400 crank journal.
As you can see on this cast example, the rods are directional too. Note the bevel on the right side of the bearing to allow space for the radius of the crank. A common beginner problem is installation of the rods backwards. Sometimes the machine shop will even press the piston on the rod backwards, so you should always check.
This 455 HO build-up will employ the new Viton BOP seal in place of the factory rope seal. The Viton seal promises to cure leakage problems associated with the rope seal and increase longevity. A groove in the cap and the block accepts the seal. First, test fit seal by installing it dry into the block and cap grooves. Then install the cap and torque it to see how the seal ends mate and make adjustments as necessary. Then the anti rotational holes in the cap are filled with high temp RTV Red. Jim also added a light coat in the groove under each seal. Before it begins to set up, the BOP seal is installed by pressing it into the groove in the block and the main cap. Care is taken to make sure the seal is pressed completely and evenly into the groove. The crank is then set into place and the main caps are installed and torqued and left to sit overnight for the sealer to cure.
Old timers will recognize this connecting rod on sight. It is a 1957 forged steel rod. They were very popular for swapping years ago until many hobbyists found out the hard way that these rods were pretty soft as they came from the factory. Some rate as low as 16 on the Rockwell C scale for hardness. Why would Taylor use this rod in this 455 HO? Because after employing a new type of heat treating called vacuum heat treating the rods now Rockwell at 37.26 on the C scale. (The rods are then checked for straightness and center to center length.) There are other advantages to these rods too ...
... Not only are they very light at 806 grams (a factory cast rod weighs 948 grams), they provide very tight side to side clearance (.019) when compared to aftermarket forged steel rods (.028) for better oil control. And they have a provision for spurt oiling from the big end of the rod to the opposite cylinder wall to reduce wear. You can see it here inside the big end and in the mirror that reflects the outside of the rod. Cast rods had this provision too but it stopped around 1970 according to Taylor. Note even the shape of the rod bolt heads differs from the "football" heads used on later cast rods. You can also see the very wide parting line of the rod, which identifies it as a forging instead of a casting.
Another feature is direct oiling of the pin bushing as you can see with the port in the top of the rod, which aids traditional splash oiling of the pins. Yes, these rods used full-floating piston pins in 1957 and they will in this engine. They have been resized (after a new bushing was pressed in) with the ARP bolts installed.
For anyone who has rebuilt a 455, these TRWs probably look familiar as they are very popular for these applications. The .030 over forged aluminum pistons feature double valve reliefs and weigh in at 596 grams. Note that they are marked for a direction of installation. They are made to be press-fit to the rods. If you use press-fit pins on your engine, be sure to double check that the machine shop installed the rod on the piston in the proper direction as discussed earlier. Also check the pistons for burrs or nicks, especially in the ring groove area, that could cause problems later.
So now you are saying, "How can these press-fit pistons be used on full-floating pin rods?" Here's how. Jim had the machine shop cut the needed grooves in each piston pin hole to retain the JE pin locks, which are shown here being installed with snap ring pliers. The piston pins were shortened to allow the space for the locks and now weigh 173 grams. Note that the pin was lubed prior to installation on the rod.
Next the ring gaps are set. Jim uses Sealed Power piston rings, which feature a chrome-moly faced 5/32 top, 1/16 cast-iron second ring and a medium tension 3/16 oil ring. Ring gaps are set relative to heat generated. This street engine calls for .019 top and .015 for the second ring. A piston has been installed and squared in the bore to provide a flat surface to get a gap reading. "If the piston ring is just placed in the bore it is difficult to square it and you may end up with a false reading," Taylor said.
The rings are cut to get the desired end gap on a ring grinder, as shown. Take just a little material off at a time and remeasure because once you go too far, that's it. Edges are then deburred with a fine grit stone to dress it, to ensure that they don't dig into the cylinder wall or piston..
Each rod bolt is completely coated with ARP Assembly Lube. Even the rod caps under the nut are coated. This is to ensure a smooth pull on the torque wrench, thereby eliminating tight spots and false torque readings.
With the top, second and oil rings installed on the pistons and the gaps in each ring clocked 180 apart (follow manufacturer's specs), the piston is oiled on the skirt only and installed using the proper tool. It's tapped into place with the wood handle of a hammer as demonstrated on a 400 engine. The rod journal is oiled with 30 weight and the end of the rod is indexed to the journal and then slid over it.
Instead of torquing the rod bolts, a bolt-stretch gauge is used. ARP recommends this method in the instructions but also provides directions for using a torque wrench. The bolt-stretch gauge is installed with the pointed ends fit into the depressions in the top and bottom of the bolt. The gauge is then preloaded and set to "0." The nut is tightened, while watching the gauge, until the dial reads .008 to indicate eight thousandths stretch. If you don't have this gauge, pull the nuts to 50 lbs.- ft., and loosen and pull to 50 two more times for a total of three with a torque wrench.
Rod side clearance is then measured with a feeler gauge slid between the rods. Bearing clearances, like the mains, were measured at the machine shop using the inside mic on the rods with bearings installed and the outside mic on the journals. Shown is a 400 block with cast rods, which requires .015-.017 clearance. As stated, the forged rods that we used required only .018, which is tight for a forged piece.
Piston to deck height can be measured two ways after locating top-dead-center. The quickest is to place a straight edge across the deck and use a feeler gauge between it and the piston to get a measurement, as shown on this 400. (Top-dead-center can be located using a positive stop, or by a much easier method of using the dial indicator alone. See below.)
Another method of measuring piston to deck height is to use a dial indicator on a magnetic base. Find top-dead-center by mounting the magnetic base of the dial indicator on the deck and place the pointer of the indicator on the piston with the piston coming up the bore. Turn the crank while watching the gauge. The needle will continue in one direction until TDC is reached. It will stop for a few degrees of dwell at TDC as you continue to turn the crank and then the needle will move in the opposite direction as the piston begins its descent. Go back to where the needle stops before changing direction and you are at TDC. Then with some preload, set the dial indicator to "0." Next, lift up the pointer of the indicator and twist the magnetic base so that the pointer will now rest on the deck when you release it. The reading on the indicator when the pointer is resting on the deck is the piston to deck height. Of course you can use a depth gauge but these two methods are quick and easy. Check the next issue for our continuing saga.